The Invention relates to a fastening element for double glass panels.
DE 40 11 229 discloses a fastening element for anchoring in a facing panel, which fastening element consists of a threaded bolt having an expansion cone arranged at its forward end, onto which expansion cone there can be pushed an annular expansion element. In order to prevent the fastening element from coming out of the drilled hole when it is being anchored in the thin-walled facing panels, anchoring takes place in an undercut drilled hole, allowing high pull-out loads whilst the anchoring is virtually free of pressure of expansion.
In order to centre the threaded bolt in the drilled hole, a spacing element is provided, which at the same time ensures that the expansion element pushed onto the expansion cone is not displaced. The spacing element has a flange, which rests against the external surface of the facing panel, as a result of which the fastening element is tensioned when a nut is screwed up on the threaded bolt; the tensioning provides support for the fastening element so that transverse forces are taken up.
Because of the high tensioning force required to provide support for the fastening element, on the one hand, and because the expansion element, which is made from metal, bears directly against the wall of the drilled hole, on the other hand, the known fastening element is not suitable for fastening double glass panels, for example for cladding buildings.
The invention is accordingly based on the problem of providing a fastening element that is suitable for anchoring in glass panels and for the fastening thereof.
When the fastening element is designed in accordance with the present invention, it eliminates the above mentioned problem.
By means of the cap, which is made from soft plastics material and which is placed over the end face of the threaded bolt and the expansion element, direct contact between the expansion element, which is made from steel, and the glass surface is avoided. The cap, which is, for example, made from polyurethane, is resiliently and/or plastically deformable so that rigid loading at a point, which can in certain circumstances result in the glass breaking, is replaced by soft, irregularity-compensating loading over an area. Because of the resulting more uniform distribution of pressure over a larger area, high loading values can be achieved with the fastening element according to the invention, even in glass.
The portion engaging in the hole drilled in the rear glass panel and providing an abutment for the expansion element forms a shoulder on the spacing sleeve, which shoulder rests against the rear glass panel without exerting pressure. The spacing sleeve passes completely through the front glass panel so that, when the nut is screwed up for fixing the fastening element, the force of reaction is completely taken up by means of the spacing sleeve. Because there are no pressure forces acting on either the rear or the front glass panel when the fastening element is being anchored, the fastening element according to the invention is suitable for fastening double glass panels wherein the two panes are arranged spaced apart from one another. Because the spacing sleeve is given support by means of the portion engaging in the hole drilled in the rear glass panel and by its outer surface in the hole drilled in the front glass panel, the spacing sleeve also assumes the task of taking up transverse forces acting on the double glass panel.
In a further embodiment of the invention, the spacing sleeve can have a flange lapping over the hole drilled in the front glass panel. The spacing between the underside of the flange and the shoulder of the spacing sleeve resting against the rear glass panel is so selected that, when the fastening element is tightened, no pressure is exerted on the front pane of glass. The flange serves merely for additional sealing of the hole drilled in the front pane of glass and to extend the area for the nut to rest against. In order to improve sealing, one or more annular sealing ribs can be arranged on the underside of the flange. Such sealing, which can optionally be further improved using appropriate sealing means, is especially advantageous when the fastening element is used for fastening insulating glass panels.